Continuing advances in wireless communications and MEMS (Micro-Electro Mechan- ical Systems) technologies have fostered the construction of a wide variety of sensor and ad hoc networks. These networks have broad applications spanning wide ar- eas, such as environmental monitoring, infrastructure maintenance, traffic manage- ment, energy management, disaster mitigation, personal medical monitoring, smart building, as well as military and defence. While these applications require high per- formance from the network, they suffer from resource constraints (such as limited battery power, processing capability, buffer space, etc.) that do not appear in tra- ditional wired networks. The inherent infrastructure-less characteristic of the sensor and ad hoc networks creates significant challenges. This dissertation addresses these challenges with two protocol designs. The main contributions of this dissertation are the design and evaluation of CS- MAC (stands for CDMA Sensor MAC), a novel multi-channel media access control (MAC) protocol for direct sequence code division multiple access (DS-CDMA) wire- less sensor networks. Our protocol design uses combination of DS-CDMA and fre- quency division to reduce the channel interference and consequently improves system capacity and network throughput. We provide theoretical characterisation of the mean multiple access interference (MAI) at a given node in relation to the number of frequency channels. We show that by using only a small number of frequency chan- nels, the mean MAI can be reduced significantly. Through discrete event simulation (using UC Berkerly NS-2 simulator), we provide comparison of our proposed system to a pure DS-CDMA system as well as a contention based system. Simulation results reveal that our proposed system can achieve significant improvement in system efi ciency (measured in packet/second/channel) of a contention based system. When the same number of packets are transmitted in the network, our system consumes much less communication energy compared to the contention based system. A distributed channel allocation protocol is also proposed for the network forma- tion phase. We prove that our algorithm converges with correct channel assignments. Simulation results reveal that a much smaller number of channels is required than theoretical value when nodes are uniformly randomly deployed. The second contribution of this dissertation involves the design and evaluation of two location-aware select optimal neighbour (SON) algorithms for CSMA/CA based MAC protocol for wireless ad hoc networks. Both algorithms concentrate on the improvement of energy eficiency of the whole network through the optimisation of the number of neighbours of each node. Our algorithms not only consider radio electronic energy consumption (e.g., coding, decoding) and radio transmission energy consumption (e.g., power amplifier), but also the electronic energy consumption at those irrelevant receivers (those who are not addressed by the transmission) that are located within the transmission range. Through simulations, we show that our algorithms can achieve signi??cant energy savings compared to the standard IEEE 802.11.
| Identifer | oai:union.ndltd.org:ADTP/234934 |
| Date | January 2005 |
| Creators | Liu, Bao Hua (Michael), Computer Science & Engineering, Faculty of Engineering, UNSW |
| Publisher | Awarded by:University of New South Wales. School of Computer Science and Engineering |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Bao Hua (Michael) Liu, http://unsworks.unsw.edu.au/copyright |
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